This disclosure relates to wireless communications.
Wireless communication devices typically use power amplifiers to amplify signals prior to over the air transmission. The efficiency of a power amplifier generally impacts the performance of devices such as a mobile phone or a base station. For a mobile phone, a higher efficiency power amplifier can increase battery life. For a base station, a higher efficiency power amplifier can reduce power consumption, which results in lower operating costs. However, high efficiency power amplifiers are typically nonlinear in power output response. Nonlinear amplification may cause spectral regrowth (e.g., a transmission mask violation) and in-band distortion (e.g., error vector magnitude (EVM) degradation). Wireless communication devices can perform power amplifier linearization to cancel nonlinear characteristics of a power amplifier. Various examples of linearization include feedback, feedforward, and predistortion techniques. Digital predistortion techniques can include polynomial based method and look-up table based methods.
Wireless communication devices can use one or more wireless communication technologies such as orthogonal frequency division multiplexing (OFDM). In an OFDM based wireless communication system, a data stream is split into multiple data substreams. Such data substreams are sent over different OFDM subcarriers, which can be referred to as tones or frequency tones. Wireless communication devices can communicate based on one or more wireless standards such as Worldwide Interoperability for Microwave Access (WiMAX), Bluetooth, or wireless local area network (WLAN) standards such as IEEE 802.11 standards. Various examples of wireless communication devices include mobile phones, smart phones, wireless routers, wireless hubs, base stations, and access points. In some cases, wireless communication electronics are integrated with data processing equipment, such as laptops, personal digital assistants, and computers